Amorphous metal alloy medical devices

ABSTRACT

This invention provides a new class of medical devices and implants comprising amorphous metal alloys. The medical devices and implants may be temporary or permanent and may comprise other materials as well, such as polymers, ceramics, and conventional crystalline or polycrystalline metal alloys. 
     Specifically, this invention provides implantable surgical fabrics comprising amorphous metal alloys. The presence of amorphous metal alloys in these fabrics can serve a variety of purposes, including structurally reinforcing the surgical fabric and/or imparting to the fabric the ability to shield against harmful radiation. The fabric may be used inside or outside the body during medical procedures. Further, the implantable surgical fabrics may be woven or non-woven fabrics.

RELATED APPLICATIONS

This application is a divisional of Ser. No. 10/607,604 filed Jun. 27,2003. The entirety of this priority application is hereby incorporatedin toto by reference.

FIELD OF THE INVENTION

This invention relates to medical devices containing at least oneamorphous metal alloy. This invention also relates to temporary andpermanent implantable devices that contain at least one amorphous metalalloy.

BACKGROUND OF THE INVENTION

It has become common to treat a variety of medical conditions byintroducing an implantable medical device partly or completely into thepatient's body. Implantable medical devices are commonplace today intreating cardiac dysfunction, orthopedic conditions, and many othertypes of conditions requiring surgical intervention. Implantable medicaldevices fall within two broad categories: permanent and temporarydevices. Temporary devices may be later removed from the body or made ofbioabsorbable materials that disappear with time without being removed.

Materials used to make both permanent and removable temporary devicesoften must be made of strong materials which are capable of deforming orbending in accordance with the pressures and movements of the patient'sbody or the organ in which they are implanted. Current metals havelimited fatigue resistance and some suffer from sensitivity to in vivooxidation. Also, because of the fabrication methods used, many metaldevices do not have acceptably smooth, uniform surfaces. This propertyis important to prevent an adverse response of the device in the body,and to prevent accelerated corrosion of the implanted device. Thus, itis desirable to produce these medical devices with a new material, i.e.,one that is non-corrosive, highly elastic, and strong.

One object of the invention relates to producing a medical implantdevice which is more resistant to repeated deformation when it is usedor implanted in the body.

Another object of the invention relates to a medical implant which iscorrosion resistant and highly biocompatible.

Yet another object of the invention relates to a medical device which isdurable enough to withstand repeated elastic deformation.

SUMMARY OF THE INVENTION

The present invention relates to a medical device containing at leastone amorphous metal alloy. Such medical devices provide the advantage ofcorrosion resistance, resistance to unwanted permanent deformation, andradiation protection. Many medical devices can benefit from suchenhanced physical and chemical properties. Implants, radiation shields,surgical devices/materials, dental prostheses, and many other similardevices are a few examples of such medical devices.

In one embodiment, the present invention provides temporary or permanentmedical implants comprising at least one amorphous metal alloy. As usedherein, an “implant” refers to an article or-device that is placedentirely or partially into an animal, for example by a surgicalprocedure. This invention contemplates implants that consist of anamorphous metal alloy component (or components) only, as well asimplants comprising at least one amorphous metal alloy componentcombined with components made of other materials, with biocompatiblematerials being particularly preferred.

The medical devices may contain one or more amorphous metal alloys. Suchalloys provide improved tensile strength, elastic deformationproperties, and reduced corrosion potential to the devices. Manydifferent types of devices may be formed of or contain amorphous metalalloys. Non-limiting examples include grafts, surgical valves, joints,threads, fabrics, fasteners, sutures, artificial sheets for heartvalves, stents and the like.

The medical devices of the present invention are preferably preparedusing a process that includes chill block melt spinning. In a preferredembodiment, the chill block melt spinning process comprises the steps ofheating an alloy in a reservoir to a temperature 50-100° C. above itsmelting temperature to form a molten alloy, forcing the molten alloythrough an orifice by pressurizing the reservoir to a pressure of about0.5-2.0 psig, and impinging the molten alloy onto a chill substrate,wherein the surface of the chill substrate moves past the orifice at aspeed of between 300-1600 meters/minute.

DETAILED DESCRIPTION OF THE INVENTION

Amorphous metal alloys, also known as metallic glasses, are disorderedmetal alloys that do not have long-range crystal structure. Manydifferent amorphous metal alloy compositions are known, includingbinary, ternary, quaternary, and even quinary alloys. Amorphous metalalloys and their properties have been the subject of numerous reviews(see for example, Amorphous Metal Alloys, edited by F. E. Luborsky,Butterworth & Co, 1983, and references therein).

Amorphous metal alloys have been used in the past primarily for itemssuch as computer-related parts, golf club heads, and drill bit coatings.All these are articles made by the so-called bulk process. However, thepresent invention has recognized that amorphous metal alloys made in acontinuous hot extrusion process, as described herein, possess physicaland chemical properties which make them attractive candidates for use inmedical devices. For example, amorphous metal alloys may have a tensilestrength that is up to tenfold higher than that of their conventionalcrystalline or polycrystalline metal counterparts. Also, amorphous metalalloys may have a tenfold wider elastic range, i.e., range of localstrain before permanent deformation occurs. These are important featuresin medical devices to provide an extended fatigue-resistant lifespan fordevices that are subjected to repeated deformations in the body. Inaddition, these features allow production of smaller or thinner devicesthat are as strong as their bulkier conventional counterparts.

Many different methods may be employed to form amorphous metal alloys. Apreferred method of producing medical devices according to the presentinvention uses a process generally known as heat extrusion, with thetypical product being a continuous article such as a wire or a strip.The process does not involve additives commonly used in the bulk processthat can render the amorphous metal alloy non-biocompatible and eventoxic. Thus, the process can produce highly biocompatible materials. Inpreferred embodiments, the continuous amorphous metal alloy articles arefabricated by a type of heat extrusion known in the art as chill blockmelt spinning. Two common chill block melt spinning techniques thatproduce amorphous metal alloy articles suitable for the medical devicesof the present invention are free jet melt-spinning and planar flowcasting. In the free jet process, molten alloy is ejected under gaspressure from a nozzle to form a free melt jet that impinges on asubstrate surface. In the planar flow method, the melt ejection crucibleis held close to a moving substrate surface, which causes the melt to bein simultaneously in contact with the nozzle and the moving substrate.This entrained melt flow damps perturbations of the melt stream andthereby improves ribbon uniformity. (See e.g., Liebermann, H. et al.,“Technology of Amorphous Alloys” Chemtech, June 1987.) Appropriatesubstrate surfaces for these techniques include the insides of drums orwheels, the outside of wheels, between twin rollers, and on belts, as iswell known in the art.

Suitable planar flow casting and free-jet melt spinning methods forproducing amorphous metal alloy components for the medical devices ofthis invention are described in U.S. Pat. Nos. 4,142,571; 4,281,706;4,489,773, and 5,381,856; all of which are hereby incorporated byreference in their entirety. For example, the planar flow castingprocess may comprise the steps of heating an alloy in a reservoir to atemperature 50-100° C. above its melting temperature to form a moltenalloy, forcing the molten alloy through an orifice by pressurizing thereservoir to a pressure of about 0.5-2.0 psig, and impinging the moltenalloy onto a chill substrate, wherein the surface of the chill substratemoves past the orifice at a speed of between 300-1600 meters/minute andis located between 0.03 to 1 millimeter from the orifice. In embodimentsinvolving free jet melt spinning, the process may comprise the steps ofheating an alloy in a reservoir to a temperature above the melting pointof the alloy, ejecting the molten alloy through an orifice in thereservoir to form a melt stream with a velocity between 1-10meters/second, and impinging the melt stream onto a chill substrate,wherein a surface of the chill substrate moves past the orifice at aspeed of between 12-50 meters/second.

Besides quenching molten metal (e.g., chill block melt spinning),amorphous metal alloys can be formed by sputter-depositing metals onto asubstrate, ion-implantation, and solid-phase reaction. Each of thesemethods has its advantages and disadvantages. The choice of a particularmethod of fabrication depends on many variables, such as processcompatibility and desired end use of the amorphous metal alloy article.

Amorphous metal alloys exhibit significantly different physicalproperties compared to normal metals, owing to their disordered localmicrostructure. In contrast to normal metals, which typically containdefects such as grain boundaries and cavities, amorphous metal alloystypically exhibit a uniform random phase on a microscopic scale, and donot contain such defects. As a result, amorphous metal alloys do notexperience the strains associated with grain boundaries and/or cavities,and therefore show superior mechanical properties, such as a highelastic modulus, high tensile strength, hardness, and fatigueresistance.

Additionally, many studies have indicated that amorphous metal alloyhave superior corrosion resistance compared to their crystallinecounterparts. (See Amorphous Metal Alloys, edited by F. E. Luborsky,Butterworth & Co, 1983, p. 479.) In particular, some amorphous metalalloys are known to resist corrosion even by anodic polarization instrongly acidic solutions (e.g., 12 M HC1).

This invention provides a new class of medical devices and implantscomprising amorphous metal alloys manufactured by heat extrusion. Theamorphous metal alloys contemplated by this invention possess theadvantages of almost any desired alloy combination, no toxic additives,and corrosion resistance that results in drastic improvement inbio-compatibility. These amorphous metal alloys have many propertiesthat make them suitable for use as implants, including high mechanicalstrength, resistance to fatigue, corrosion resistance, andbiocompatibility. The implants of this invention may be implanted inanimals, non-limiting examples of-which include reptiles, birds, andmammals, with humans being particularly preferred. Besides containing atleast one amorphous metal alloy, the implants of this invention mayoptionally contain other materials, including different types ofamorphous metal alloys, conventional crystalline or polycrystallinemetals or metal alloys, polymers, ceramics, and natural and syntheticbiocompatible materials.

The devices of this invention may be implanted into a body in differentways, including, but not limited to subcutaneous implantation,implantation at the surface of the skin, implantation in the oralcavity, use as sutures and other surgical implantation methods.

The devices may contain one or more amorphous metal alloys. The methodof heat extrusion is very flexible and many combinations of metals canbe made into an amorphous metal alloy. By way of example, iron-based,cobalt-based alloys, copper-based amorphous metal alloys, as well asothers may be manufactured using heat extrusion as described herein. Incertain embodiments, the amorphous metal alloys may comprise ametalloid, non-limiting examples of which include silicon, boron, andphosphorus. One possible amorphous metal alloy is an Fe—Cr—B—P alloy.Many other similar alloys are suitable and known to one of ordinaryskill in the art.

In certain preferred embodiments, the amorphous metal alloyscontemplated by this invention exhibit significantly lower conductanceor are non-conductive, compared to their crystalline or polycrystallinecounterparts.

In some embodiments of the invention, amorphous metal alloy componentsfor implants may be used, i.e. parts of the implant are made ofamorphous metal alloys. These parts may be provided in a variety ofways. For example, the component may be produced by machining orprocessing amorphous metal alloy stock (e.g., a wire, ribbon, rod, tube,disk, and the like). Amorphous metal alloy stock made by chill blockmelt spinning can be used for such purposes.

The amorphous metal alloy components of this invention may optionally becombined or assembled with other components, either amorphous metal orotherwise, in order to form the implants of this invention. For example,the amorphous metal alloy components may be combined with abiocompatible polymer or ceramic, a biodegradable polymer, a therapeuticagent (e.g., a healing promoter as described herein) or another metal ormetal alloy article (having either a crystalline or amorphousmicrostructure).

The method of combining or joining the amorphous metal alloy componentsto other components can be achieved using methods that are well known inthe art. Non-limiting examples of joining methods including physicaljoining (e.g., braiding, weaving, crimping, tying, and press-fitting)and joining by adhesive methods (e.g., gluing, dip coating, and spraycoating). Combinations of these methods are also contemplated by thisinvention.

The implants of this invention may be temporary or permanent medicalimplants and comprise at least one amorphous metal alloy component. Asused herein, an “implant” refers to an article or device that is placedentirely or partially into an animal, for example by a surgicalprocedure or minimally invasive methods. This invention contemplatesboth implants that consist of an amorphous metal alloy component (orcomponents) only, as well as implants containing amorphous metal alloycomponents combined with components made of other materials, withbiocompatible materials being preferred. Many different types ofimplants may be formed of or contain amorphous metal alloys.Non-limiting examples include grafts, surgical valves, joints, threads,fabrics, fasteners, sutures, stents and the like.

One aspect of this invention is to provide an implantable surgicalfastener containing at least one amorphous metal alloy. The surgicalfastener may be a monofilament or multifilament suture that optionallyhas a coating, such as a resorbable polymer and/or a healing promoter.The implantable surgical fastener may also be a clamp, clip, sheath,staple, or the like. Other embodiments of surgical fasteners includeamorphous metal alloy wires performing as artificial ligaments ortendons.

Another aspect of this invention is to provide a surgical fabriccomprising at least one amorphous metal alloy. The fabric may be wovenor non-woven. In some embodiments, the surgical fabric is a non-wovenfabric which is made of a non-woven polymeric sheet and at least oneamorphous metal alloy thread, wire, or foil that is bonded or laminatedthereto. In other embodiments, the surgical fabric is a woven fabriccontaining at least one amorphous metal alloy thread, fiber or foilwhich may be combined with fibers or threads of another material. Thewoven fabric may contain a plurality of polymeric threads interwovenwith at least one amorphous metal alloy thread. The amorphous metalalloy threads optionally include a coating, such as a polymer coating ora healing promoter.

The surgical fabric of this invention may be implanted into a body as aprosthetic device or a part of a prosthetic device. Alternatively, thesurgical fabric may be used outside the body, for example, as a part ofa device to shield a patient from radiation.

Yet another aspect of this invention is to provide an artificial heartcomponent, such as an artificial heart valve or a pacemaker, wherein theartificial heart component includes an amorphous metal alloy component.In some embodiments, the artificial heart valve is a ball valvecomprising an amorphous metal alloy cage. In other embodiments theartificial heart valve can include leaves made of amorphous metal alloy.The amorphous metal alloy component may also be a sheath or a strut. Thepacemaker containing the amorphous metal alloy may house an energysource which is shielded from the body by the amorphous metal alloy.

This invention also provides a stent, graft, or like device wherein thedevice includes a tube, sheath or coiled wire containing an amorphousmetal alloy.

One aspect of this invention is to provide a stent-graft comprising asubstantially tubular member containing an amorphous metal alloy and agraft material attached to the substantially tubular member. The graftmaterial optionally comprises a surgical fabric containing an amorphousmetal alloy with the advantage of making it stronger or alternativelythinner for a given desired strength than conventional materials.

The present invention also provides orthopedic implant devicescontaining an amorphous metal alloy components. The implants may be usedfor reconstructive surgery. In some embodiments, the orthopedic implantmay contain wires and sheets to perform as ligaments/tendons, springs,tissue growth limiters and the like.

In other embodiments of this invention, the orthopedic implant is anartificial joint containing an amorphous metal alloy. The artificialjoint may be a ball-in-socket joint, knee joint or elbow joint orligament/tendon replacements in such locations.

Those of ordinary skill in the art will recognize that many types ofmedical devices, such as, for example, implants or implant componentsare possible based on the teachings and disclosure of this patent.Accordingly, the following examples are to be viewed as merelyillustrative of the concept of the invention, and are by no meanslimiting.

EXAMPLE 1 Sutures Comprising Amorphous Metal Alloys

This invention provides implants comprising amorphous metal alloys forreconstructive surgery. One aspect of this invention provides surgicalfasteners comprising amorphous metal alloy. The term “surgicalfastener”, as used in this context, refers to an implantable device thatcan be used-to hold tissue in place. Non-limiting examples of suchfasteners include clamps, clips, sheaths, sutures, and staples. Thesurgical fasteners may be temporary (e.g., removable staples that aid inthe closing of a surgical incision but are removed when the tissue ishealed) or permanent (e.g., a clip fastened to a bone to restore theproper position of a displaced ligament or tendon).

Amorphous metal alloys are suitable because of their high mechanicalstrength, resistance to in vivo oxidation and corrosion, and overallbiocompatibility. The surgical fasteners may be made by heat extrusionmethods described above. In certain embodiments, the surgical fastenerof this invention consists of an amorphous metal article that can bedirectly implanted into a living creature. Alternatively, the surgicalfastener may be combined with other components such as biodegradablepolymers and/or therapeutic agents (e.g., thrombosis or fibrinolyticinhibitors) to promote healing.

In certain embodiments of this invention, the surgical fasteners aresutures. A good suture material must meet demanding mechanical andbiological requirements. For example, the tensile strength of a suturematerial, which is defined as the number of pounds of tension that thesuture will withstand before it breaks when knotted or fixed in someother way, must be able to withstand not only the strain caused by thejoining of the tissues to be sutured, but also any additional strainscaused by the inevitable movement by the patient. This is particularlycritical when the suture material is used to suture tissues having ahigh natural tension, such as fasciae or tendons. In addition to meetingstringent mechanical requirements, a good suture material should bebiologically inert and should elicit a minimal tissue reaction from thepatient, if at all. Excess tissue reaction is known to promote infectionand retard healing.

Suture materials can be classified under various categories. Forexample, a suture material can be made from a single strand of material(“monofilament”) or made from several filaments that are joined together(“multifilament”), typically by methods such as braiding or twisting.Monofilament sutures tie smoothly and are less likely to harbormicroorganisms, but can be prone to knot slippage. Multifilamentsutures, on the other hand, typically have good handling and tyingqualities, but can harbor microorganisms.

This invention provides sutures comprising amorphous metal alloys. Thesutures may be monofilament sutures comprising a single strand ofamorphous metal alloy filament. In certain embodiments, the monofilamentamorphous metal alloy sutures also comprise an additional sheath orcoating (e.g., an absorbable polymer coating) which modifies thebiological or mechanical properties of the monofilament suture. Forexample, the coaling or sheath may be used to prevent or to reduce knotslippage, to improve the biocompatibility, or to modify the chemicalproperties of the surface of the suture.

Alternatively, the sutures may be multifilament sutures comprising atleast one amorphous metal alloy filament. In certain embodiments, themultifilament sutures comprise at least one amorphous metal alloyfilament that is joined (e.g., via braiding or twisting) with polymericfilaments. Such polymeric filaments may be made from inert,non-biodegradable materials or resorbable polymers according to methodsthat are well known in the art. Alternatively, the multifilament suturesof this invention may be made by braiding or twisting together aplurality of amorphous metal alloy filaments, without any polymericfilaments. As in the case for the monofilament sutures of thisinvention, the amorphous metal alloy filaments in the multifilamentsutures contemplated by this invention optionally may have a coating orsheath to improve or to modify the chemical, biochemical, or mechanicalproperties of the filaments.

Amorphous metal alloy filaments for such use can be made by heatextrusion methods known in the art and described herein.

The sutures contemplated by this invention may be permanent or temporarysutures. The high strength, resistance to corrosion and fatigue, andoverall biocompatibility of amorphous metal alloy filaments make suturescomprising such filaments particularly appropriate for permanentsutures. In particular, the high tensile strength of amorphous metalalloy filaments makes sutures comprising such filaments particularlysuitable for permanently joining tissue that is expected to be underconstant natural tension, such as tendons or fasciae. The use of suchsutures may also be advantageous where the diameter of the thread needsto be as small as possible. However, the use of the sutures of thisinvention as a temporary post-operative surgical fastener is alsocontemplated. The sutures of this invention may be used likeconventional non-resorbable sutures and removed when the tissue joinedby the sutures is sufficiently healed.

EXAMPLE 2 Implantable Surgical Fabrics Comprising Amorphous Metal Alloys

This invention provides implantable surgical fabrics comprisingamorphous metal alloys. The presence of amorphous metal alloys in thesefabrics can serve a variety of purposes, including structurallyreinforcing the surgical fabric and/or imparting to the fabric theability to shield against harmful radiation. The fabric may be usedinside or outside the body during medical procedures (e.g. as a fabricto cover areas of the body of the patient or operators during proceduresinvolving hazardous radiation).

The implantable surgical fabrics contemplated by this invention may bewoven or non-woven fabrics. In certain embodiments, the implantablesurgical fabrics are woven fabrics comprising both polymeric andamorphous metal alloy threads. The implantable woven surgical fabric maycomprise bare amorphous metal alloy threads, or optionally amorphousmetal alloy threads that have been treated with a coating material priorto implantation in order to improve biocompatibility and/or to promotehealing. For example, the amorphous metal alloy threads may be coatedwith at least one resorbable polymer material, non-limiting examples ofwhich include polyglycolides, polydioxanones, polyhydroxyalkanoates,polylactides, alginates, collagens, chitosans, polyalkylene oxalate,polyanhydrides, poly(glycolide-co-trimethylene carbonate),polyesteramides, or polydepsipeptides.

Alternatively, the coating material may comprise healing promoters suchas thrombosis inhibitors, fibrinolytic agents, vasodilator substances,anti-inflammatory agents, cell proliferation inhibitors, and inhibitorsof matrix elaboration or expression. Examples of such substances arediscussed in U.S. Pat. No. 6,162,537, which is hereby incorporated byreference in its entirety. This invention also contemplates using apolymer coating (e.g., a resorbable polymer) in conjunction with ahealing promoter to coat the amorphous metal alloy wires.

The polymeric threads of the woven surgical fabrics contemplated by thisinvention may be resorbable or completely inert towards biodegradation.When the polymer fibers are resorbable, the in vivo degradation of thefibers leaves behind a woven amorphous metal alloy fabric thatreinforces the injured tissue. In some embodiments of this invention,both resorbable and inert polymer threads are woven with the amorphousmetal alloy thread. In other embodiments, the polymer threads(resorbable, inert or a combination of both) are joined to an amorphousmetal alloy foil, for example, by lamination.

In certain embodiments of this invention, the surgical fabrics compriseamorphous metal alloy threads, but not polymer threads. In theseembodiments, the amorphous metal alloy threads may be bare or may becoated as described above.

The surgical fabrics of this invention may also be non-woven. Forexample, the surgical fabric may comprise at least one fluoropolymer orpolyolefin sheet that is reinforced with a plurality of amorphous metalalloy threads, a fine amorphous metal alloy mesh, or an amorphous metalalloy foil. The amorphous metal alloy threads, mesh, or foil may bebonded to one or more fluoropolymer sheets by methods that are wellknown in the art, such as lamination.

In certain embodiments of the woven and non-woven surgical fabrics ofthis invention, the amorphous metal alloy threads are added to thefabric in a non-isometric way, causing the fabric to have differentmechanical properties in different directions. For example, theamorphous metal alloy threads may be added in one direction, causing thefabric to be stiff in one direction, but soft and extendable in thetransverse direction.

The surgical fabrics contemplated by this invention may be used for avariety of purposes. For example, the surgical fabric may be fashionedinto a vascular graft, where the presence of reinforcing amorphous metalalloy threads or mesh provides better resistance to the continuouspressure caused by arterial or venous blood flow. The surgical fabricsof this invention may also be used as an endoprosthesis for repairingdefects in the abdominal wall of a mammal and for preventing theformation of hernias.

Another use of the surgical fabrics of this invention is as an internalradiation shield. For example, the surgical fabric can be used to encasean energy or radiation emitting power source, such as e.g., aradioactive power source for a medical device (e.g., a pacemaker), sothat the tissue surrounding the power source experiences minimal or nodamage from the source.

EXAMPLE 3 Stents Comprising Amorphous Metal Alloys

A stent is a tubular implant that is surgically inserted into a bodylumen, in order to widen the lumen or to ensure that the lumen remainsopen. Stents have been used for repairing many body conduits, includingthose of the vascular, biliary, genitourinary, gastrointestinal, andrespiratory systems.

Stents are typically inserted into the patient in an unexpanded form,positioned at the site to be repaired, and then expanded. To makepositioning of the stent easier, the radial dimension of the stent inits unexpanded form should be less than that of the body lumen.Additionally, a stent should have longitudinal flexibility so that itcan more easily negotiate the typically tortuous path-to the site to berepaired. To fulfill these mechanical requirements, stents may be madeof elastic materials such as spring steels, stainless steel, Nitinol,Elgiloy or inelastic materials such as tantalum, titanium, silver andgold.

This invention provides implantable stents comprising at least oneamorphous metal alloy. Amorphous metal alloys are particularly suitablestent materials for several reasons. For example, amorphous metal alloyshave a wide elastic range which makes them ideal for stents implanted inareas of the body that may be subject to outside forces afterimplantation. The material may be less traumatic due to itsnon-conductance (or low conductance) and biocompatibility. Additionally,the high strength of amorphous metal alloys may allow stents to be madeof thinner material, further decreasing trauma.

The amorphous metal alloy stents of this invention may be made accordingto designs that are well known in the art. For example, the stents maycomprise amorphous metal alloy wires that are shaped into an expandablecylindrical structure, or etched in different methods from sheets ofamorphous metal and then rolled and fastened to make a cylinder, oretched from an amorphous metal tube. The etching in these embodiments,whether flat or tubular may be by chemical etching, EDM, LASER cutting,etc. The fastening of a flat structure to a cylinder may be achieved bymethods such as fusing, mechanical locking, and the like.

The amorphous metal alloy stents of this invention may comprise othermaterials as well. In some embodiments, the stents comprise anadditional graft member that comprises a flexible, biocompatible matrixdesigned to promote incorporation of the stent into the wall of the bodylumen at the site to be repaired. The stent, graft, or both mayadditionally comprise a polymer (e.g., a resorbable polymer) or healingpromoters, non-limiting examples of which include thrombosis inhibitors,fibrinolytic agents, vasodilator substances, anti-inflammatory agents,and cell proliferation inhibitors. In certain embodiments, the amorphousmetal alloy stent may be directly coated with a polymer and/or a healingpromoter. In other embodiments, the graft comprises surgical fabricscontaining amorphous metal alloys as disclosed herein. In a preferredembodiment, the surgical fabrics fabricated such that the mechanicalproperties of the fabric are different in different directions. Forexample, the graft may be soft and extendable in the longitudinaldirection, but very stiff and non-extending in the circumferentialdirection.

EXAMPLE 4 Artificial Heart Valves Comprising Amorphous Metal Alloys

The design and fabrication of a reliable, permanent artificial heartvalve requires the careful selection of materials and the considerationof many different factors. The artificial heart valve must be able towithstand the corrosive environment within the body. This corrosiveenvironment results from the immunogenic response caused by theimplanted heart valve as well as by the presence of electrolytes in thebloodstream and surrounding tissue, which can cause metal components inthe artificial heart valve to oxidize and/or corrode. The artificialheart valve must also be constructed from a material that can withstandthe repeated strain it must undergo during up to 40,000,000 systoliccycles of closing and opening. The position of the valve in the highvolume flow of blood transforms the slightest problem inbiocompatibility into high probability of valve failure. In addition,very aggressive permanent treatment with blood thinners may becomenecessary, despite their adverse side effects.

Artificial heart valves comprising hard metals made of fixed leaves thatrotate on hinges are known. This structure is suboptimal but no metal isknown that will endure the strains existing in natural heart valves. Themetal valves also have limited lifetime due to suboptimalbiocompatibility leading to thrombosis.

For these reasons, amorphous metal alloys are attractive alternativematerials for artificial heart valves. The properties of amorphous metalalloys, such as strain resistance and biocompatibility lead toartificial heart valves with very long lifetimes. This inventionprovides an artificial heart valve comprising at least one amorphousmetal alloy component. Amorphous metal alloy components are particularlysuitable for artificial heart valves for several reasons. First,amorphous metal alloys are very biocompatible and corrosion resistant.Second, amorphous metal alloys are resistant to fatigue and creep, dueto the absence of defects such as grain boundaries and internalcavities.

This invention contemplates providing amorphous metal alloy componentsfor artificial heart valves, such as cages, flanges, hinges, rings,support struts, and sheaths and springs. The amorphous metal alloycomponents may be fabricated according to heat extrusion methods, suchas chill block melt spinning methods that are well known in the art.Additionally, the amorphous metal alloy components are used inconjunction with other materials, such as biocompatible polymeric orceramic materials, as is well known in the art.

EXAMPLE 5 Implants Comprising Amorphous Metal Alloys For ReconstructiveSurgery

This invention also contemplates orthopedic implants comprisingamorphous metal alloys. In some embodiments, the orthopedic implants arein the form of reconstructive hardware for repairing ligaments andtendons. Non-limiting examples of reconstructive hardware include wires,springs, and meshes. The reconstructive hardware may be suitablyfabricated from an amorphous metal alloy that exhibits a high fatiguelimit, resistance to plastic deformation, good biocompatibility, andresistance to oxidation and corrosion. The reconstructive hardware maybe made according to fabrication methods well known in the art, such asheat extrusion and machining.

This invention also provides implantable orthopedic prosthesescomprising an amorphous metal alloy. The orthopedic prosthesescontemplated by this invention may be an amorphous metal article usedalone or in combination with other materials, such as biocompatiblepolymers or plastics, ceramics, or other biocompatible metals.

This invention also provides tissue growth limiters comprising anamorphous metal alloy. The tissue growth limiter of this invention maycomprise other materials, such as biocompatible and/or biosorbablepolymers. In some embodiments, the tissue growth limiter is in the formof a sheath comprising amorphous metal alloys. In other embodiments, thetissue growth limiter is a fabric containing amorphous metal alloys,such as the surgical fabrics described herein.

EXAMPLE 6 Orthodontic and Dental Implants Comprising Amorphous MetalAlloys

This invention provides orthodontic implants comprising amorphous metalalloys. The orthodontic implants contemplated by this invention includepermanent implants (e.g., tissue growth limiters) as well as temporaryimplants (e.g., orthodontic wires and braces used in orthodontic bracesfor realigning teeth).

Orthodontic Wires and Brackets

The wires that are used in orthodontic braces must meet demandingmechanical and chemical requirements. For example, the wire must be ableto resist breakage during the initial insertion step when the wire isfastened to a metal band or anchor that is fixed to a tooth. Once inplace, the wire must be able to withstand the constant tension set bythe orthodontist as well as the repeated mechanical stress caused whenthe patient eats. Additionally, the wire must not be susceptible tocorrosion, even when the patient consumes acidic or salty foods.

Currently, several types of orthodontic wire materials are known.Stainless steel has been the predominant choice for use as wires in mostorthodontic braces. However, other metals and metal alloys have foundniche applications. For example, wires made of cobalt-chromium alloyscan be manufactured to provide variable material stiffness.Additionally, a titanium-molybdenum alloy known as beta-titanium can beused to provide a moderately stiff wire that is more stiff thannickel-titanium wires but less stiff than stainless steel wires.

Some alloys used for orthodontic treatments are known to have certaindrawbacks. For example, it has been reported that beta-titanium wireshave a tendency to break when they are bent or twisted during clinicaltreatment. This tendency may result from defects such as microcracks orinclusions. Furthermore, nickel-chromium alloys, while strong even inthin cross-section, can cause abutting teeth to discolor.

This invention provides amorphous metal alloy wires for the controlledmovement of teeth using conventional orthodontic braces. Amorphous metalalloy wires are particularly useful because they are highly resistant tofatigue, biocompatible, and corrosion-resistant. Additionally, amorphousmetal alloys are known to have a high elastic modulus. Accordingly,because the wires are more resistant to stretching under tension, it iseasier to maintain constant tension on the teeth, leading to reducedtreatment times.

The amorphous metal alloys wires may be made by techniques well known inthe art and are commercially available. The wires can be inserted intoconventional orthodontic hardware (e.g., brackets or clamps) in the samemanner as the wires that are currently known in the art.

This invention also provides orthodontic brackets and clamps comprisingamorphous metal alloys. The brackets may be made according to designsthat are well known in the art by methods such as machining. In apreferred embodiment of the invention, the brackets and clamps are usedin conjunction with orthodontic wires comprising an amorphous metalalloy as described herein.

Tissue Growth Limiters

This invention provides tissue growth limiters comprising an amorphousmetal alloy for oral or orthodontic implants. In some embodiments, thetissue growth limiter exclusively consists of an amorphous metal alloyarticle, while in other embodiments, an amorphous metal alloy article iscombined with other biocompatible and/or biosorbable materials.Non-limiting examples of tissue growth limiters contemplated by thisinvention include sheaths, meshes, and fabrics, such as the surgicalfabrics described herein.

I claim:
 1. An implantable surgical fabric comprising a non-woven sheetreinforced with an amorphous metal alloy throughout the surgical fabric,wherein the non-woven sheet comprises a plurality of amorphous metalalloy threads.
 2. The implantable surgical fabric according to claim 1,wherein the amorphous metal alloy threads include a coating.
 3. Theimplantable surgical fabric according to claim 2, wherein the coatingcomprises a polymeric material.
 4. The implantable surgical fabricaccording to claim 3, wherein the polymeric material is a resorbablepolymer.
 5. The implantable surgical fabric according to claim 4,wherein the resorbable polymer comprises an element selected from thegroup consisting of polyglycolides, polydioxanones,polyhydroxyalkanoates, polylactides, alginates, collagens, chitosans,polyalkylene oxalate, polyanhydrides, poly(glycolide-co-trimethylenecarbonate), polyesteramides, and polydepsipeptides.
 6. The implantablesurgical fabric according to claim 2, wherein the coating comprises ahealing promoter.
 7. The implantable surgical fabric according to claim6, wherein the healing promoter is selected from the group consisting ofthrombosis inhibitors, fibrinolytic agents, vasodilator substances,anti-inflammatory agents, cell proliferation inhibitors, inhibitors ofmatrix elaboration, and inhibitors of matrix expression.
 8. Theimplantable surgical fabric according to claim 2, wherein the coatingcomprises a polymeric material and a healing promoter.
 9. Theimplantable surgical fabric according to claim 1, wherein said amorphousmetal alloy comprises an element selected from the group consisting ofsilicon, boron, and phosphorous.
 10. The implantable surgical fabricaccording to claim 1, wherein said amorphous metal alloy is aniron-based alloy containing Fe, Cr, B, and P.